Since the invention of the laser, there has been a great deal of interest in second-harmonic (SH) generation as a technique for obtaining coherent light at short wavelengths from long wavelength laser sources. Research in this field is driven primarily by the need for efficient methods of up converting infrared light from conventional solid-state and semiconductor laser sources to the visible wavelength range. In particular, the wide spread use of optical memory storage (e.g. compact disks) has created a demand for reliable short wavelength light sources to increase storage density. However, there has also been considerable interest in developing coherent signal detectors and processors which rely on SH or sum-frequency (SF) generation. M. M. Fejer, G. A. Magel, D. H. Jundt, and R. L. Byer, in an article entitled "Quasi Phase Matched Second-Harmonic Generation: Tuning and Tolerances", IEEE J. Quantum Electron., vol. 28, pp. 2631-2654, 1992 describe the use of quasi-phase matching (QPM) in dielectric waveguides for high efficiency SH generation.
R. Normandin, the applicant, R. L. Williams, and F. Chatenoud, in an article entitled "Enhanced Surface Emitting Waveguides For Visible, Monolithic Semiconductor Laser Sources", in Electron. Lett., vol. 26. pp. 2088-2089, 1990 describe the use of semiconductor waveguides as a means for high efficiency SH generation. However, to date there has been little exploration of SH generation in semiconductor heterostructures designed for propagation of the fundamental and SH light approximately perpendicular to the layers. Recently, such heterostructures have become increasingly important in other branches of optoelectronics; examples include vertical-cavity surface-emitting lasers (VCSELs), modulators, and optical switches. Since the material-light interaction in vertical propagation devices is enhanced using multiple reflections, as opposed to long interaction lengths in waveguide devices, device size is only limited by the transverse mode width of the light beam which is typically only a few .mu.m.